"Our security forces must not stop until everyone involved in the orchestration and execution of today's massacre in St. Philip's Catholic Church is brought to book by the strong arm of justice".
President Muhammadu Buhari has condemned the Ozubulu Church attack in Anambra State by a yet to be identified gunmen, describing the incident as "an appalling crime against humanity and unspeakable sacrilege".
Witness Chukwuma Emeka told AFP news agency he had just stepped out of the church to stretch his legs "when I heard gunshots and screaming and people running inside".
There were varying accounts of what happened in Ozubulu.
The source reportedly said some worshippers who were critically injured died on their way to the Nnamdi Azikiwe Teaching Hospital in Nnewi, the state capital.
Confirming the number of the casualties, Umar said 11 peopled were confirmed dead.
He said the gunmen then went on rampage and "shot at the remaining worshippers numbering over 100".
According to him, intelligence report linked the shooting to an existing feud existing between some members of Umuezekwe Ofufe Amakwa community of Ozubulu living overseas.
"The information at the disposal of the police is that the gunman had been hired to kill a particular family person believed to be among the worshippers", he said.
He said that preliminary investigations by the police revealed that the attack was carried out by a native of the area.
In his reaction, Victor Oye, the National Chairman, All Progressives Grand Alliance, APGA, said that no amount of provocation could justify the killing of innocent people who had gone to worship in a Church.
The Speaker of the House of Representatives, Honourable Yakubu Dogara has also expressed displeasure over the attack, describing it as abominable, barbaric and inhuman.
"Today, my heart goes out to Nigeria's Christian community, Gov. Willy Obiano, the people of Anambra and the families of the victims and the survivors of this bad massacre".